Understanding Deep Vein Thrombosis

Deep vein thrombosis (DVT) is a condition in which a blood clot or thrombus forms in a deep vein. A blood clot is most common in the leg. But it can develop in a large vein deep inside the leg, arm, or other part of the body. Part of the clot called an embolus can separate from the vein. It may travel to the lungs and form a pulmonary embolus (PE). This can cut off blood flow to part of the lung or to the entire lung. A PE is a medical emergency and may cause death. Healthcare providers use the term venous thromboembolism (VTE) to describe the 2 conditions, DVT and PE. They use the term VTE because the 2 conditions are very closely related. And, because their prevention and treatment are closely related.

Over time, a blood clot can also permanently damage veins. To protect your health, a blood clot must be treated right away.

How DVT develops

The deep veins of the legs are located in the muscles. These help carry blood from the legs to the heart. When leg muscles contract and relax, blood is squeezed through the veins back to the heart. One-way valves inside the veins help keep the blood moving in the right direction. When blood moves too slowly or not at all, it can pool in the veins. This makes a clot more likely to form.

Cross section of muscle and vein showing open valve with arrow showing blood moving up. Cross section of varicose vein with thrombus and emboli.

Risk factors

Anyone can get a blood clot. These risk factors make a blood clot more likely to happen:

  • Being inactive for a long time, such as when you’re in the hospital, or traveling by plane or car

  • Injured vein due to an accident, a broken bone, or surgery

  • Past blood clots 

  • Personal or family history of a blood-clotting disorder

  • Recent surgery

  • Cancer and certain cancer treatments

  • Smoking

Other things can also put you at higher risk for a blood clot. They include:

  • Being older than 60

  • Pregnancy

  • Taking birth control or hormone replacement

  • Having other vein problems

  • Being a person of size

Common symptoms

A blood clot doesn't always cause obvious symptoms. If you do have symptoms, they often happen suddenly. They may include:

  • Pain, especially deep in the muscle

  • Swelling

  • Aching or soreness

  • Red or warm skin

  • Fever

When to call your healthcare provider

Call your healthcare provider if you have any of the common symptoms listed above. In addition, call your provider if you have symptoms of bleeding such as:

  • Blood in the urine
  • Bleeding with bowel movements
  • Bleeding from the nose, gums, a cut, or the vagina

Call 911

Call 911 if you have symptoms of pulmonary embolism such as:

  • Trouble breathing

  • Fast heartbeat

  • Chest pain

  • Sweating

  • Coughing (may cough up blood)

  • Fainting

If you take medicine to help prevent blood clots, you have an increased risk of bleeding. Also call 911 if you have heavy or uncontrolled bleeding.

Diagnosing DVT

Your healthcare provider will start with questions about your symptoms and health history along with a physical exam.

Diagnostic tests include:

  • An imaging test called a duplex ultrasound. This test uses sound waves to create pictures of veins and blood flow.

  • Blood tests. These are done to check for clotting and other problems.

If your provider thinks you may have pulmonary embolism, more testing will be done.

Treating DVT

Treating a blood clot may include:

  • Medicine to thin the blood and prevent pulmonary embolism and other complications.

  • Staying in the hospital. This may or may not be needed.

  • Surgery in some cases.

Preventing DVT

Many people who are in the hospital are at an increased risk of developing blood clots. So, preventing blood clots is an important part of in-hospital care. The care may include getting out of bed regularly, taking medicine, or using special therapies or devices. Other factors and conditions may increase the risk of blood clots. Review your risk with your healthcare provider.